A dual-temperature-source underground energy storage device

Abstract

The application provides a double-temperature-source underground energy storage device, and relates to the technical field of energy storage, comprising a low-temperature source heat storage system, a high-temperature source heat storage system and a medium transfer assembly. The low-temperature source heat storage system comprises a low-temperature heat storage tank, an organic working medium R245fa circulating loop and an organic Rankine cycle power generation component, and is suitable for a 100-150 DEG C heat source; the high-temperature source heat storage system comprises a high-temperature heat storage tank, a pressurized water circulating loop and a steam turbine power generation component, and is suitable for a >=200 DEG C heat source; a two-way circulating pump realizes medium cross-system transfer; and a control and monitoring system regulates and controls the operation mode. The application realizes multi-grade heat source partitioned heat storage and graded power generation, improves the heat-electricity conversion efficiency, supports multi-element heat source access, and optimizes the underground deployment space utilization and protection.

Description

Technical Field

[0001] This invention relates to the field of energy storage technology, specifically to a dual-temperature-source underground energy storage device. Background Technology

[0002] With the increasing demand for waste heat recovery in the industrial sector and the large-scale development of renewable energy sources such as solar and geothermal energy, heat sources of various temperatures and grades have become an important part of the energy system. Among them, medium and low temperature heat sources of 100-150℃ are widely found in industrial flue gas, solar collectors, and low-grade geothermal energy, while high temperature heat sources above 200℃ are commonly found in incineration exhaust gas, chemical reaction heat, and high-grade geothermal energy. The emergence of these multi-temperature heat sources has placed higher demands on the comprehensive utilization of energy.

[0003] However, existing underground energy storage technologies generally rely on single-temperature-grade heat source designs, making it difficult to achieve efficient and coordinated recovery of waste heat across multiple temperature ranges. On the one hand, traditional systems often employ decentralized processing schemes, leading not only to fragmented energy utilization but also to high equipment redundancy and increased upfront investment costs. On the other hand, the heat storage medium is not optimized for different temperature ranges, and the power generation modules are mostly single-cycle forms such as steam turbines or organic Rankine cycles, lacking a dual-temperature-source coordination mechanism. This results in poor temperature matching between the heat source and the power generation system, and the heat-to-electricity conversion efficiency remains at a low level.

[0004] Although dual-source energy storage can theoretically achieve precise temperature matching through tiered thermal storage and power generation, existing devices are limited by factors such as insufficient performance of the thermal storage medium and unreasonable system coupling design, making it impossible to simultaneously achieve high efficiency and high flexibility. They are also difficult to adapt to mixed heat sources of multiple grades, such as industrial waste heat and renewable energy. Therefore, there is an urgent need for an innovative device that can achieve tiered thermal storage, precise matching of power generation cycles, and safe underground deployment, in order to break through the current technical bottlenecks in the utilization of multiple grades of energy. Summary of the Invention

[0005] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a dual-temperature-source underground energy storage device that enables zoned thermal storage of multiple heat sources of different grades.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A dual-temperature-source underground energy storage device, comprising:

[0008] A low-temperature heat storage system includes a low-temperature heat storage tank, a first heat exchanger, and a second heat exchanger; a first loop of the first heat exchanger is connected to the low-temperature heat storage tank, and a second loop is connected to the first loop of the second heat exchanger; a first working fluid pump is installed on the pipeline between the low-temperature heat storage tank and the first heat exchanger; a turbine and a second working fluid pump are installed on the pipeline between the first heat exchanger and the second heat exchanger.

[0009] The high-temperature heat storage system includes a high-temperature heat storage tank, a third heat exchanger, and a fourth heat exchanger; the first loop of the third heat exchanger is connected to the high-temperature heat storage tank, and the second loop is connected to the first loop of the fourth heat exchanger; a third working fluid pump is installed on the pipeline between the high-temperature heat storage tank and the third heat exchanger; a steam turbine and a fourth working fluid pump are installed on the pipeline between the third heat exchanger and the fourth heat exchanger.

[0010] The cold source is connected to the second circuit of the second and fourth heat exchangers;

[0011] A bidirectional circulation pump is connected between the low-temperature thermal storage tank and the high-temperature thermal storage tank.

[0012] Preferably, the low-temperature heat storage tank is connected to a low-temperature waste heat source; the high-temperature heat storage tank is connected to a high-temperature waste heat source.

[0013] Preferably, the low-temperature source thermal storage system uses organic working fluid R245fa as the heat transfer medium.

[0014] Preferably, the high-temperature source heat storage system uses pressurized hot water as the heat transfer medium.

[0015] Preferably, both the low-temperature thermal storage tank and the high-temperature thermal storage tank are filled with an energy storage medium; the energy storage medium is a boric acid-succinic acid eutectic material with a molar ratio of 6:4.

[0016] Preferably, the cryogenic thermal storage tank is equipped with a plurality of first liquid level sensors, which are arranged in an array at equal intervals along the height direction of the cryogenic thermal storage tank; the first liquid level sensors are used to monitor the height of the liquid energy storage medium inside the cryogenic thermal storage tank.

[0017] Preferably, the high-temperature thermal storage tank is equipped with multiple second liquid level sensors; the second liquid level sensors are used to monitor the height of the liquid energy storage medium inside the high-temperature thermal storage tank.

[0018] Preferably, the second liquid level sensor is a high-temperature resistant liquid level sensor.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention utilizes a partitioned design of a low-temperature source thermal storage system and a high-temperature source thermal storage system to adapt to two types of heat sources: medium-low temperature and high temperature. The low-temperature system employs an organic working fluid R245fa cycle, matched with an organic Rankine cycle for power generation, while the high-temperature system employs a pressurized water cycle, matched with a steam turbine for power generation. This achieves a precise correspondence between "different temperature heat sources - dedicated thermal storage medium - adapted power generation cycle," solving the problem of poor temperature matching in traditional single systems and maximizing the utilization of multiple heat sources.

[0021] The system uses a boric acid-succinic acid eutectic material with a molar ratio of 6:4 as the energy storage medium. This material can achieve latent heat storage through solid-liquid phase change in the low-temperature range, and can also combine sensible heat and thermochemical heat storage to form a three-mode heat storage in the high-temperature range. Compared with traditional phase change materials, it significantly improves the energy storage density and provides support for efficient heat storage and stable heat release.

[0022] The reversible transfer of the thermal storage medium between the low-temperature tank and the high-temperature tank is achieved through a bidirectional circulation pump. During the thermal storage stage, the medium in the low-temperature tank can be scheduled according to the power generation needs of the high-temperature source. During the heat release stage, the high-temperature source thermal storage system can be prioritized to meet the peak power generation needs, and the low-temperature source thermal storage system can supplement the basic load or backup power. At the same time, it supports the access of multiple heat sources such as industrial waste heat, solar energy, and geothermal energy, thus solving the problem of insufficient adaptability of traditional systems.

[0023] Both low-temperature and high-temperature thermal storage tanks are designed to be buried 5-10m underground, with an external aerogel insulation layer and a polyurethane moisture-proof layer. The pipelines are made of seamless stainless steel, which reduces the occupation of surface space, controls heat loss, adapts to the underground humid environment, and improves the protection and concealment of the facilities. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention.

[0025] in:

[0026] 1. Low-temperature waste heat source; 2. Low-temperature thermal storage tank; 3. First liquid level sensor; 4. First working fluid pump; 5. First heat exchanger; 6. Second working fluid pump; 7. Turbine; 8. Second heat exchanger; 9. Cold source; 10. Two-way circulation pump; 11. High-temperature waste heat source; 12. Second liquid level sensor; 13. High-temperature thermal storage tank; 14. Third working fluid pump; 15. Third heat exchanger; 16. Fourth working fluid pump; 17. Steam turbine; 18. Fourth heat exchanger. Detailed Implementation

[0027] The invention will now be further described with reference to the accompanying drawings.

[0028] like Figure 1 As shown, a dual-source underground energy storage device includes a low-temperature source thermal storage system and a high-temperature source thermal storage system; both the low-temperature source thermal storage system and the high-temperature source thermal storage system use a heat transfer medium to transfer and conduct heat.

[0029] Low-temperature source thermal storage system (100~150) oC) Includes a cryogenic heat storage tank 2, a first working fluid pump 4, a first heat exchanger 5, a turbine 7, a second heat exchanger 8, and a second working fluid pump 6; the cryogenic heat storage tank 2 is connected to a cryogenic waste heat source 1; the first circuit of the first heat exchanger 5 is connected to the cryogenic heat storage tank 2, and the second circuit is connected to the first circuit of the second heat exchanger 8; the first working fluid pump 4 is connected to the pipeline between the cryogenic heat storage tank 2 and the first heat exchanger 5; the first working fluid pump 4 is used to pump the heat transfer medium between the cryogenic heat storage tank 2 and the first heat exchanger 5, so that the heat in the cryogenic heat storage tank 2 is transferred to the first heat exchanger 5; the turbine 7 and the second working fluid pump 6 are connected to the pipeline between the first heat exchanger 5 and the second heat exchanger 8; the second working fluid pump 6 is used to pump the heat transfer medium between the first heat exchanger 5 and the second heat exchanger 8, so that the heat in the first heat exchanger 5 is transferred to the turbine 7.

[0030] High-temperature source thermal storage system (200 o The system includes a high-temperature heat storage tank 13, a third working fluid pump 14, a third heat exchanger 15, a steam turbine 17, a fourth heat exchanger 18, and a fourth working fluid pump 16. The high-temperature heat storage tank 13 is connected to a high-temperature waste heat source 11. The first loop of the third heat exchanger 15 is connected to the high-temperature heat storage tank 13, and the second loop is connected to the first loop of the fourth heat exchanger 18. The third working fluid pump 14 is connected to the pipeline between the high-temperature heat storage tank 13 and the third heat exchanger 15. The third working fluid pump 14 is used to pump the heat transfer medium between the high-temperature heat storage tank 13 and the third heat exchanger 15, so that the heat in the high-temperature heat storage tank 13 is transferred to the third heat exchanger 15. The steam turbine 17 and the fourth working fluid pump 16 are connected to the pipeline between the third heat exchanger 15 and the fourth heat exchanger 18. The fourth working fluid pump 16 is used to pump the heat transfer medium between the third heat exchanger 15 and the fourth heat exchanger 18, so that the heat in the third heat exchanger 15 is transferred to the steam turbine 17.

[0031] Both the low-temperature heat storage tank 2 and the high-temperature heat storage tank 13 are filled with energy storage medium; the second circuits of the second heat exchanger 8 and the fourth heat exchanger 18 are both connected to a cold source 9; the cold source 9 is used to cool the heat transfer medium in the second heat exchanger 8 and the fourth heat exchanger 18; a bidirectional circulation pump 10 is connected between the low-temperature heat storage tank 2 and the high-temperature heat storage tank 13.

[0032] Furthermore, the low-temperature source thermal storage system uses organic working fluid R245fa as the heat transfer medium.

[0033] Furthermore, the high-temperature source thermal storage system uses pressurized hot water as the heat transfer medium.

[0034] Furthermore, the energy storage medium is a boric acid-succinic acid eutectic material with a molar ratio of 6:4; its temperature range is 100~150℃. o C undergoes a solid-liquid phase change (latent heat storage); 200 oAbove C, based on its three-mode characteristics of sensible heat, latent heat and thermochemical heat storage, it achieves sensible heat, latent heat and thermochemical heat storage through molecular structure adjustment, with a total heat storage density as high as 394 J / g.

[0035] The bidirectional circulation pump 10 is used to transport the liquid boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 to the high-temperature heat storage tank 13, thereby realizing the reversible transfer of the heat storage medium to the high-temperature source heat storage system.

[0036] Furthermore, the cryogenic thermal storage tank 2 is equipped with multiple first liquid level sensors 3, which are arranged in an array at equal intervals along the height direction of the cryogenic thermal storage tank 2; the first liquid level sensors 3 are used to monitor the height of the liquid energy storage medium inside the cryogenic thermal storage tank 2.

[0037] Furthermore, multiple second liquid level sensors 12 are installed inside the high-temperature thermal storage tank 13; the second liquid level sensors 12 are used to monitor the height of the liquid energy storage medium inside the high-temperature thermal storage tank 13.

[0038] Furthermore, the second liquid level sensor 12 is a high-temperature resistant liquid level sensor.

[0039] How to run:

[0040] (1) Low-temperature thermal storage

[0041] Low-temperature waste heat source 1 (such as industrial waste gas or wastewater at 100~150℃) exchanges heat with organic working fluid R245fa through a conventional heat exchanger, causing R245fa to heat up and partially vaporize.

[0042] The vaporized R245fa transfers heat to the boric acid-succinic acid eutectic phase change material inside the cryogenic storage tank 2. During the heat absorption process, this material transforms from a solid to a liquid state, effectively absorbing residual heat through the latent heat of the solid-liquid phase change, thus achieving long-term storage of low-grade thermal energy.

[0043] The cryogenic thermal storage tank 2 is equipped with first liquid level sensors 3 at different heights to monitor the phase change process in real time. When the liquid level stops rising, it indicates that the eutectic material has completed the solid-liquid transformation, and the thermal storage process is over. By reasonably controlling the circulation flow rate and heat exchange area, it can be ensured that the phase change material fully absorbs heat and successfully completes melting and thermal storage.

[0044] (2) Low-temperature power generation (organic Rankine cycle)

[0045] When energy storage needs to be released, the first working fluid pump 4 drives the R245fa in the first loop of the first heat exchanger 5 to circulate between the cryogenic storage tank 2 and the first heat exchanger 5. At this time, the boric acid-succinic acid eutectic material in the cryogenic storage tank 2 gradually solidifies, releasing latent heat and transferring the heat to the first heat exchanger 5. Subsequently, the second loop of the first heat exchanger 5 uses this heat to heat the R245fa organic working fluid, causing it to evaporate into high-pressure steam and enter the turbine 7 to expand and do work, driving the generator to generate electricity.

[0046] The expanded R245fa working fluid is cooled and condensed by the second heat exchanger 8, and then returned to the first heat exchanger 5 by the second working fluid pump 6, forming a closed loop, thereby realizing the energy release and low-temperature waste heat power generation of the low-temperature thermal storage system.

[0047] (3) High-temperature thermal storage

[0048] The molten liquid energy storage medium (boric acid-succinic acid eutectic phase change material) in the low-temperature thermal storage tank 2 is transported to the high-temperature thermal storage tank 13 via a bidirectional circulation pump 10. High-temperature waste heat source 11 (such as flue gas at 300-500℃, kiln exhaust gas, etc.) heats the pressurized water via a heat exchanger, raising its temperature to above 200℃ and forming saturated or superheated steam. The pressurized steam then acts as a heat transfer medium, transferring heat to the high-temperature thermal storage tank 13.

[0049] Inside the high-temperature thermal storage tank 13, the boric acid-succinic acid eutectic phase change material can not only store heat through sensible and latent heat, but also undergo a reversible thermochemical reaction within the range of 160~200℃. Specifically, boric acid decomposes endothermically into metaboric acid and water; during the exothermic process, the reaction can proceed in reverse, causing metaboric acid and water to recombine into boric acid, thereby releasing the heat of chemical reaction. Thus, the boric acid-succinic acid eutectic phase change material achieves synergistic storage of sensible heat, latent heat, and thermochemical energy, belonging to a "three-modal" energy storage material.

[0050] Therefore, by utilizing the "three-modal" characteristics of this material, the boric acid-succinic acid eutectic material in the high-temperature thermal storage tank 13 can be further heated to ≥200℃, effectively achieving high-density storage of high-grade thermal energy and providing a stable heat source for subsequent high-temperature power generation.

[0051] (4) High-temperature power generation (steam-turbine power generation)

[0052] When power is required, the third working fluid pump 14 starts, driving the pressurized water in the first loop of the third heat exchanger 15 to circulate between the high-temperature heat storage tank 13 and the third heat exchanger 15. During the circulation process, the pressurized water absorbs the heat released by the boric acid-succinic acid eutectic material in the high-temperature heat storage tank 13 and transfers it to the second loop of the third heat exchanger 15.

[0053] During this process, the heat storage medium gradually solidifies from a liquid state, releasing latent heat; simultaneously, metaboric acid reacts with water in a reverse reaction to regenerate boric acid, further releasing the heat of chemical reaction. This heat is transferred to the second loop of the third heat exchanger 15, heating the pressurized water in the second loop of the third heat exchanger 15 and evaporating it into high-temperature, high-pressure steam.

[0054] High-pressure pressurized steam is pumped to the turbine 17 via the fourth working fluid pump 16, where it expands and performs work, driving the turbine to power a generator and output electrical energy. The expanded steam then enters the fourth heat exchanger 18, where it is cooled into pressurized water, and flows back to the third heat exchanger 15, forming a closed-loop water-steam cycle system. Through this cycle, the high-temperature thermal energy storage unit can stably release stored energy and efficiently convert energy into power generation.

[0055] (5) Collaborative operation

[0056] When the system operates in peak-valley regulation mode, the high-temperature thermal energy storage system is prioritized to provide peak power output to meet peak grid load demand. The low-temperature thermal energy storage system is used to provide base load power, ensuring the continuity and stability of power output. During load fluctuations, the low-temperature system can also serve as a backup power source to supplement the high-temperature system, preventing grid power supply interruptions. By coordinating the operation of the two systems through the control system, both low-temperature waste heat can be fully utilized, and high-temperature waste heat can be efficiently utilized, achieving stable power output and flexible dispatch.

[0057] Implementation method:

[0058] Low-temperature thermal energy storage-power generation process:

[0059] S1, the heat from the low-temperature waste heat source 1 (industrial low-temperature waste heat, solar heat collection) is transferred to the low-temperature heat storage tank 2 through the organic working fluid R245fa;

[0060] S2. The boric acid-succinic acid eutectic material in the low-temperature thermal storage tank 2 absorbs heat and undergoes a solid-liquid phase transition, completing a 100~150°C change. o Thermal storage in zone C;

[0061] S3. The liquid level sensor monitors the liquid medium level in the cryogenic heat storage tank 2 in real time to determine the heat storage progress.

[0062] S4. The first working fluid pump 4 drives the organic working fluid R245fa to circulate between the low temperature heat storage tank 2 and the first heat exchanger 5, transferring heat to the first heat exchanger 5.

[0063] S5. The low-boiling-point working fluid absorbs heat in the first heat exchanger 5 and then enters the turbine 7 to do work and generate electricity.

[0064] S6. The working fluid after performing work is cooled by the cold source 9 through the second heat exchanger 8, and then sent back to the first heat exchanger 5 through the second working fluid pump 6 to complete the organic Rankine cycle.

[0065] High-temperature thermal energy storage and power generation process:

[0066] S1. The bidirectional circulation pump 10 transports the liquefied boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 to the high-temperature heat storage tank 13.

[0067] S2. The heat from the high-temperature waste heat source 11 (medium-high temperature industrial waste heat, geothermal energy) is transferred to the high-temperature heat storage tank 13 through pressurized water.

[0068] S3, the eutectic material in the high-temperature thermal storage tank 13 further absorbs heat using its three-mode thermal storage characteristics, raising the temperature to 200°C. o Temperatures above 30°C are used to complete high-temperature heat storage.

[0069] S4, the third working fluid pump 14 drives pressurized water to circulate between the high-temperature heat storage tank 13 and the third heat exchanger 15 to transfer high-temperature heat;

[0070] S5. Pressurized water absorbs heat in the third heat exchanger 15 and then enters the steam turbine 17 to generate electricity.

[0071] S6. The water after doing work is cooled by the cold source 9 through the fourth heat exchanger 18, and then sent back to the third heat exchanger 15 through the fourth working fluid pump 16 to complete the turbine 17 cycle.

[0072] Key equipment parameters:

[0073] Low-temperature thermal storage tank 2: 2m in diameter, 4m in height, pressure ≥0.6MPa, with one set of first liquid level sensors 3 installed every 0.8m along the height inside the tank to monitor the liquid medium level;

[0074] High-temperature thermal storage tank 13: 2.5m in diameter, 5m in height, pressure ≥2.5MPa, with a high-temperature resistant second liquid level sensor 12 inside the tank to monitor the medium status;

[0075] Organic Rankine Turbine 7: Compatible with R245fa refrigerant, rated power 500kW, inlet temperature 150℃ o C;

[0076] Steam Turbine 17: Suitable for pressurized water, rated power 1500kW, inlet temperature 250℃ o C;

[0077] Two-way circulating pump 10: Flow rate adjustable (5~10m³ / h) 3 / h), high temperature resistance ≥180 o C enables bidirectional transport of media.

[0078] Control logic:

[0079] Thermal storage stage: When high-temperature waste heat power generation is required and the liquid medium in the low-temperature thermal storage tank 2 accounts for 95%, the bidirectional circulation pump 10 is triggered to start and transport the medium to the high-temperature thermal storage tank 13.

[0080] Heat release phase: Depending on the power generation demand, the cryogenic system and the high-temperature system can operate independently or in coordination (the high-temperature system is prioritized to meet high power demand, while the cryogenic system supplements the base load).

[0081] Underground deployment of steam

[0082] Low-temperature thermal storage tank 2 and high-temperature thermal storage tank 13 are buried underground (5~10m deep), and are covered with a 5cm thick aerogel insulation layer + an 8cm thick polyurethane moisture-proof layer. The heat loss is controlled to ≤3% per month.

[0083] The system piping is made of seamless stainless steel, and the low-temperature piping can withstand 150°C. o C / 0.6MPa, high-temperature pipeline withstands 300 o C / 3MPa, suitable for damp underground environments.

Claims

1. A dual-temperature-source underground energy storage device, characterized in that, include: The low-temperature heat storage system includes a low-temperature heat storage tank, a first heat exchanger, and a second heat exchanger. The low-temperature heat storage tank is connected to a low-temperature waste heat source. The first loop of the first heat exchanger is connected to the low-temperature heat storage tank, and the second loop is connected to the first loop of the second heat exchanger. A first working fluid pump is installed on the pipeline between the low-temperature heat storage tank and the first heat exchanger. A turbine and a second working fluid pump are installed on the pipeline between the first heat exchanger and the second heat exchanger. The low-temperature heat storage system uses organic working fluid R245fa as the heat transfer medium. The high-temperature heat storage system includes a high-temperature heat storage tank, a third heat exchanger, and a fourth heat exchanger. The high-temperature heat storage tank is connected to a high-temperature waste heat source. The first loop of the third heat exchanger is connected to the high-temperature heat storage tank, and the second loop is connected to the first loop of the fourth heat exchanger. A third working fluid pump is installed on the pipeline between the high-temperature heat storage tank and the third heat exchanger. A steam turbine and a fourth working fluid pump are installed on the pipeline between the third heat exchanger and the fourth heat exchanger. The high-temperature heat storage system uses pressurized hot water as the heat transfer medium. The cold source is connected to the second circuit of the second and fourth heat exchangers; A two-way circulation pump is connected between the low-temperature heat storage tank and the high-temperature heat storage tank; Both the low-temperature and high-temperature thermal storage tanks are filled with an energy storage medium; the energy storage medium is a boric acid-succinic acid eutectic material. Low-temperature thermal energy storage-power generation process: S1. The heat from the low-temperature waste heat source is transferred to the low-temperature heat storage tank through the organic working fluid R245fa. S2. The boric acid-succinic acid eutectic material inside the low-temperature thermal storage tank absorbs heat and undergoes a solid-liquid phase transition, completing a 100~150°C change. o Thermal storage in zone C; S3. The liquid level sensor monitors the liquid medium level in the cryogenic thermal storage tank in real time to determine the thermal storage progress. S4. The first working fluid pump drives the organic working fluid R245fa to circulate between the low-temperature heat storage tank and the first heat exchanger, transferring heat to the first heat exchanger. S5. The low-boiling-point working fluid absorbs heat in the first heat exchanger and then enters the turbine to do work and generate electricity. S6. After the work is done, the working fluid is cooled by the cold source through the second heat exchanger, and then pumped back to the first heat exchanger through the second working fluid pump to complete the organic Rankine cycle. High-temperature thermal energy storage and power generation process: S1. The bidirectional circulation pump transports the liquefied boric acid-succinic acid eutectic material in the low-temperature thermal storage tank to the high-temperature thermal storage tank. S2. The heat from the high-temperature waste heat source is transferred to the high-temperature heat storage tank through pressurized water; S3. The eutectic material inside the high-temperature thermal storage tank further absorbs heat by utilizing the three-modal thermal storage characteristics of sensible heat, latent heat, and thermochemical heat storage, raising the temperature to 200°C. o Temperatures above 30°C are used to complete high-temperature heat storage. S4. The third working fluid pump drives pressurized water to circulate between the high-temperature heat storage tank and the third heat exchanger, transferring high-temperature heat. S5. Pressurized water absorbs heat in the third heat exchanger and then enters the steam turbine to generate electricity. S6. After the water has done its work, it is cooled by the cold source through the fourth heat exchanger and then pumped back to the third heat exchanger through the fourth working fluid pump to complete the turbine cycle.

2. The dual-temperature-source underground energy storage device as described in claim 1, characterized in that, The molar ratio of the boric acid-succinic acid eutectic material is 6:

4.

3. The dual-temperature-source underground energy storage device as described in claim 1, characterized in that, The cryogenic thermal storage tank is equipped with multiple first liquid level sensors, which are arranged in an array at equal intervals along the height direction of the cryogenic thermal storage tank; the first liquid level sensors are used to monitor the height of the liquid energy storage medium inside the cryogenic thermal storage tank.

4. The dual-temperature-source underground energy storage device as described in claim 1, characterized in that, The high-temperature thermal storage tank is equipped with multiple second liquid level sensors; the second liquid level sensors are used to monitor the height of the liquid energy storage medium inside the high-temperature thermal storage tank.

5. The dual-temperature-source underground energy storage device as described in claim 4, characterized in that, The second liquid level sensor is a high-temperature resistant liquid level sensor.

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